Emergency call support for VoLTE roaming within S8 home routing architecture

ABSTRACT

A method, a device, and a non-transitory storage medium provide an emergency call support service in which a network device of a visited network obtains user profile data of a wireless device from a home network of the wireless device, and provides the user profile data to a location server of the visited network. The emergency call support service allows an emergency call, when initiated by a roaming subscriber of the wireless device via the visited network, to include the user profile data and be provided to a public safety access point.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/953,949 filed on Nov. 30, 2015, the disclosure of which isincorporated herein by reference in its entirety.

Background

Long Term Evolution (LTE) Service providers that provide Voice over LTE(VoLTE) wish to offer the VoLTE service to their subscribers not only inthe subscribers' home country but also in a visited network. Forexample, when the subscriber roams into a visited network that does notoffer LTE coverage, the subscriber may fall back to a circuit-switched(CS) technology afforded by a second generation (2G) network or a thirdgeneration (3G) network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an exemplary environment in whichexemplary embodiments of an emergency call support service may beimplemented;

FIGS. 2A-2J are diagrams that illustrate exemplary processes pertainingto the emergency call support service;

FIG. 3 is a diagram illustrating exemplary components of a device thatmay correspond to one or more of the devices in the exemplaryenvironment; and

FIG. 4 is a flow diagram that illustrates an exemplary processpertaining to the emergency call support service.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description refers to the accompanying drawings.The same reference numbers in different drawings may identify the sameor similar elements. Also, the following detailed description does notlimit the invention.

According to a Third Generation Partnership Project (3GPP) technicalreport (e.g., TR 23.749 0.01.0; Release 14), a new architecture calledS8 Home Routing (also referred to as S8HR) has been proposed directed toVoLTE roaming. As with any new architecture, S8HR must meet certainregulatory requirements, such as lawful interception and data retention,as well as support for emergency calls. The S8HR architecture does notuse local breakout (LBO) but uses a Packet Date Network Gateway (PGW) ofa Home Public Land Mobile Network (HPLMN) as an Internet ProtocolMultimedia Subsystem (IMS) Access Point Name (APN) rather than a networkdevice of a Visitor Public Land Mobile Network (VPLMN). Additionally,the S8HR architecture does not provide a Network-to-Network Interface(NNI) between network elements of a home IMS and a visited IMS.

According to an exemplary implementation of the S8HR architecture, thehome IMS is used for VoLTE calls while the visited IMS is used foremergency calls since emergency calls are to be connected to localemergency services. However, in an emergency call context, the visitedIMS is unable to obtain the Mobile Station International SubscriberDirectory Number (MSISDN) of the visiting user equipment (UE) placingthe emergency call (e.g., a 911 call) because there is not an NNIbetween the visited IMS and a Home Subscriber Server (HSS) of a homeIMS. Consequently, the visited IMS is unable to communicate the MSISDNof the visiting UE to an emergency call server (ECS) and the ECS isunable to communicate a callback number to a Public Safety Access Point(PSAP). As a result, if the emergency call is disconnected for anyreason, the PSAP will not have a callback number so as to re-establishthe emergency call with the visiting UE/visiting user.

According to an exemplary embodiment, an emergency call support serviceis provided, as described herein. According to an exemplary embodimentof the emergency call support service, when a visiting UE attaches to avisited network, a visited mobility management entity (MME) obtains userprofile data from the HSS of a home network of the visiting UE. The userprofile data includes the MSISDN of the visiting UE/visiting user.According to various embodiments, the visiting MME provides the userprofile data to one or multiple location servers of the visitingnetwork. According to an exemplary implementation, the visiting MMEprovides the user profile data to the location server during attachmentof the visiting UE. According to another exemplary implementation, thevisiting MME provides the user profile data to the location server inresponse to an emergency call being initiated by the visiting UE.According to yet another exemplary implementation, the visiting MMEprovides the user profile data to the location server in response to aquery from the location server. According to various implementations,the user profile data may be provided to the location server via a pushmethod, via a pull method, and so forth, as described herein.

According to an exemplary embodiment of the emergency call supportservice, during emergency call establishment, in addition to obtaininglocation data, an ECS queries the location server to obtain the userprofile data, which includes the MSISDN of the visiting UE and/orvisiting user. According to an exemplary embodiment, the ECS providesthe user profile data and the location data to a PSAP.

In view of the foregoing, the emergency call support service allows anemergency call with callback data, which is initiated from a roamingVoLTE subscriber, to be established and maintained in the S8HRarchitecture.

FIG. 1 is a diagram illustrating an exemplary environment 100 in whichexemplary embodiments of an emergency call support service may beimplemented. As illustrated, environment 100 includes a home network 101and a visited network 131. Environment 100 further includes a wirelessdevice 175 and a user 180.

Home network 101 includes an evolved Node B (eNB 105-1), a servinggateway (SGW) 110-1, a PGW 115-1, an MME 120-1, an HSS 125, and a homeIMS 130. Visited network 131 includes an eNB 105-2, an SGW 110-2, a PGW115-2, an MME 120-2, an HSS 125-2, an ECS 127, a PSAP 135, a GatewayMobile Location Center (GMLC) 140, and a visited IMS 165.

ENB 105-1 is a network element of an exemplary home access network. ENB105-2 is a network element of an exemplary visited access network. Forexample, the home and visited access networks may be implemented as anEvolved Universal Mobile Telecommunications System (UMTS) TerrestrialRadio Access Network (E-UTRAN) of an LTE network or an LTE-Advancednetwork.

SGW 110-1, PGW 115-1, MME 120-1, and HSS 125-1 are network elements ofan exemplary home Evolved Packet Core (EPC). SGW 110-2, PGW 115-2, MME120-2, and HSS 125-2 are network elements of an exemplary visitedEvolved Packet Core (EPC). The network elements of the home and visitedaccess networks and EPCs may operate according to a 3GPP specification.Additionally, as illustrated, communicative links exist between thesenetwork elements based on various interfaces (e.g., S1-MME, S1-U, etc.).

Home IMS 130 and visited IMS 165 each includes network elements of anIMS system. For example, although not illustrated, home IMS 130 andvisited IMS 165 may include a Proxy Call Session Control Function(P-CSCF), an Interrogating-CSCF (I-CSCF), a Serving-CSCF (S-CSCF), anEmergency-CSCF (E-CSCF), and so forth. Also, according to an exemplaryembodiment, there is no NNI between home IMS 130 and visited IMS 165.

ECS 127 includes a route determination function that routes an emergencycall (e.g., a VoLTE 9-1-1call) to a PSAP (e.g., PSAP 135). ECS 127includes a location retrieval function to obtain an emergency caller'slocation. For example, ECS 127 may obtain various types of location datahaving varying levels of granularity (e.g., cell identifier, GlobalPositioning System (GPS) coordinates (e.g., latitude, longitude), etc.).According to an exemplary embodiment, ECS 127 includes a callbackretrieval function that obtains an emergency caller's MSISDN. Accordingto an exemplary embodiment, ECS 127 queries a location server (e.g.,GMLC 140) for the MSISDN of wireless device 175/user 180. For example,the query may include an identifier of wireless device 175 (e.g., anInternational Mobile Station Equipment Identity (IMEI)) and/or anidentifier of user 180 (e.g., International Mobile Subscriber Identity(IMSI)). ECS 127 provides the MSISDN and an identifier (e.g., IMEI,IMSI, etc.) to PSAP 135.

PSAP 135 is a call center responsible for answering calls to anemergency telephone number. For example, PSAP 135 includes handlingVoLTE 9-1-1calls. GMLC 140 provides location-based services pertainingto mobile devices. Additionally, as illustrated, communicative linksexist between ECS 127, PSAP 135, and GMLC 140 based on variousinterfaces (e.g., Mm, Le, SLg, etc.).

Wireless device 175 includes a communicative and computational devicethat allows user 180 to place an emergency call. According to anexemplary embodiment, wireless device 175 operates according to a 3GPPLTE or LTE-A standard. Wireless device 175 may be implemented as amobile device or a portable device. By way of example, wireless device175 may be implemented as a smartphone, a tablet, a phablet, a netbook,a vehicular communication system within a vehicle, or a wearable device.Wireless device 175 may store one or multiple applications. For example,wireless device 175 may include a telephone application, a multi-mediaapplication, an e-mail application, a contacts application, a calendarapplication, an instant messaging application, a web browsingapplication, a location-based application (e.g., a Global PositioningSystem (GPS)-based application, etc.), a social networking application,a camera application, a toolbar application, and so forth. User 180 isan operator of wireless device 175.

The number of network elements, the number of networks, and thearrangement in environment 100 are exemplary. According to otherembodiments, environment 100 may include additional network elementsand/or differently arranged network elements than that illustrated inFIG. 1. Additionally, or alternatively, according to other embodiments,multiple network elements may be implemented on a single network device,and conversely, a network element may be implemented on multipledevices. Additionally, or alternatively, environment 100 may include anadditional network and/or arrangement of networks that is different fromthat illustrated in FIG. 1.

A communicative link between devices may be direct or indirect and mayinvolve an intermediary device and/or an intermediary network notillustrated in FIG. 1. For example, a communicative connection betweenwireless device 175 and eNB 105-2 may be indirect and involve othertypes of wireless nodes, such as a home eNB, a pico base station, afemto device, a relay station, etc. Additionally, the number and thearrangement of the links are exemplary.

FIGS. 2A-2J are diagrams illustrating exemplary embodiments of theemergency call support service. According to an exemplary scenario,referring to FIG. 2A, assume wireless device 175 initiates an attachmentprocedure with visited network 131 via eNB 105-2. The attachmentprocedure may include a random access procedure and a radio resourcecontrol (RRC) connection establishment procedure. After an RRCconnection is established, an authentication procedure begins. Forexample, wireless device 175 transmits authentication andsecurity-related messages 205 to MME 120-2 via eNB 105-2.Authentication/security messages 205 may include an IMEI and an IMSI. Inturn, MME 120-2 and HSS 125-1 exchange messages 207. For example, MME120-2 transmits an Authentication Information Request to HSS 125-1. Inresponse, HSS 125-1 transmits an Authentication Information Answer toMME 120-2. According to an exemplary embodiment, MME 120-2 obtains theMSISDN pertaining to user 180 from HSS 125-1.

Referring to FIG. 2B, according to one exemplary implementation, MME120-2 transmits an identifier (e.g., IMEI and/or IMSI) and the MSISDN ofuser 180 to GMLC 140, in response to obtaining the MSISDN (illustratedas ID and MSISDN 209), even though an emergency call has not beeninitiated by user 180. Depending on the number and configuration ofGMLCs 140, MME 120-2 may transmit the identifier and the MSISDN to asingle GMLC 140 or to multiple GMLCs 140. For example, when there aremultiple GMLCs 140, MME 120-2 may transmit (e.g., broadcast orindividually transmit) the identifier and the MSISDN to multiple GMLCs140. According to another example, there may be multiple GMLCs 140,however, MME 120-2 may transmit the identifier and the MSISDN to asingle GMLC 140. For example, a configuration of GMLCs 140 may be suchthat they can communicate with each other. Thus, the single GMLC 140 maypass the identifier and the MSISDN to one or multiple other GMLCs 140.According to yet another example, when there are multiple GMLCs 140, MME120-2 may transmit the identifier and the MSISDN to a single GMLC 140.However, according to this example, a configuration may be such thatthey cannot communicate with each other. In view of this configuration,ECS 127 may query multiple GMLCs 140 in order to obtain the MSISDN fromthe single GMLC 140, as described further below. Of course, when thereis only one GMLC 140, MME 120-1 may transmit the identifier and theMSISDN to the only available GMLC 140. According any of the examplesdescribed, GMLC 140 stores the identifier and the MSISDN (illustrated asstores identifier and MSISDN 211) in a database or a data structure.

Referring to FIG. 2C, according to another exemplary implementation, MME120-2 does not transmit the identifier and the MSISDN of user 180 toGMLC 140, in response to obtaining the MSISDN. Rather, MME 120-2 storesthe MSISDN. Thus, in contrast to the implementation described inrelation to FIG. 2B, MME 120-2 transmits the MSISDN to GMLC 140 only ifuser 180 places an emergency call.

Referring to FIG. 2D, subsequent to messages 207, MME 120-2 selects aPGW (illustrated as selects PGW 213) of home network 101. For example,MME 120-2 may set the information element VPLMN Dynamic Address“Allowed” to “Not Allowed.” A bearer for SIP signaling may be createdbetween SGW 110-2 and PGW 115-1. After completion of the attachmentprocedure, wireless device 175/user 180 may register with home IMS 130(illustrated as registers with home IMS 215). Home IMS 130 may providenearly all IMS services (e.g., normal voice call, video call, ShortMessaging Service (SMS), etc.). However, home IMS 130 does not provideemergency call service. According to an exemplary implementation, MME120-2 transmits an attach accept message (illustrated as attach accept217) to wireless device 175 in which the attach accept message includesan Emergency Service Support Indicator information element. Wirelessdevice 175 may use this information as a basis for determining that anemergency VoLTE call is supported by visited IMS 165.

Referring to FIG. 2E, assume user 180 places an emergency call (e.g.,dials 911) via wireless device 175 (illustrated as places an emergencycall 219). According to this example, and in view of the attachment andregistration described above, assume that user 180/wireless device 175did not register with visited IMS 165 since an NNI does not existbetween home IMS 130 and visited IMS 165. According to suchcircumstances, the emergency call may be considered an unauthenticatedor anonymous emergency call.

Wireless device 175 transmits an emergency attach request to MME 120-2(illustrated as emergency attach 221). The emergency attach requestincludes the IMEI of wireless device 175. The emergency attach requestmay also include the IMSI. As further illustrated, MME 120-2 selects aPGW so that an emergency bearer can be established (illustrated asselects PGW 223). For example, MME 120-2 selects PGW 115-2.

As previously described above in relation to FIG. 2C, MME 120-2 may nottransmit the identifier and the MSISDN to GMLC 140. In continuity withthis implementation, referring to FIG. 2F, in response to an emergencycall having been initiated by user 180, MME 120-2 transmits theidentifier and the MSISDN of wireless device 175/user 180 to GMLC 140 inone of the manners previously described (illustrated as ID and MSISDN225). Consequently, GMLC 140 stores the identifier and the MSISDN in adatabase or a data structure (illustrated as stores identifier andMSISDN 227).

Referring to FIG. 2G, subsequent to an emergency PDN connection beingestablished, wireless device 175 transmits a SIP Invite (illustrated asSIP Invite 229) that propagates to visited IMS 165. The SIP Inviteincludes an identifier (e.g., the IMEI). In response to receiving theSIP Invite, visited IMS 165 selects an ECS. For example, although notillustrated, a P-CSCF of visited IMS 165 may identify the SIP Invite aspertaining to an emergency call. In response, the P-CSCF selects anE-CSCF of visited IMS 165. The E-CSCF selects ECS 127 (illustrated asselects ECS 231). When location information is not included in the SIPInvite or additional location information is needed, the E-CSCF queriesECS 127 for routing instructions to the PSAP (illustrated as queries ECS233). The location retrieval function of ECS 127 may include a routingdetermination function (RDF) that provides the routing information(e.g., a Uniform Resource Identifier (URI) of the PSAP) to the E-CSCF.In response, the E-CSCF routes the SIP Invite to the PSAP 135.

Referring to FIG. 2H, according to an exemplary embodiment, in responseto receiving the query for routing information, ECS 127 queries GMLC 140for the MSISDN (illustrated as queries GMLC 235). Depending on thenumber of GMLCs 140, ECS 127 may transmit one or multiple queries to oneor multiple GMLCs 140. The query includes the identifier (e.g., theIMEI). In response to receiving the query, GMLC 140 performs a lookupfor the MSISDN based on the IMEI (illustrated as lookup MSISDN 237).GMLC 140 transmits a response that includes the MSISDN to ECS 127. ECS127 stores the MSISDN. According to an exemplary implementation, ECS 127provides the MSISDN to PSAP 135 in response to a request for a locationupdate from PSAP 135, as described further below. According to anotherexemplary implementation, ECS 127 transmits the MSISDN to PSAP 135 inresponse to receiving the MSISDN from GMLC 140.

Referring to FIG. 2I, according to another exemplary embodiment, ECS 127does not query GMLC 140 for the MSISDN in response to receiving thequery for routing information. Rather, ECS 127 queries GMLC 140 for theMSISDN in response to receiving a query from PSAP 135. For example, PSAP135 may query ECS 127 for a location update (illustrated as queries ECS239). In response to receiving the query from PSAP 135, ECS 127transmits one or multiple queries to obtain location data pertaining towireless device 175/user 180 and the MSISDN (illustrated as queries GMLC241). According to various implementations, ECS 127 may transmit twoqueries to GMLC 140 (i.e., one query for the location data and anotherquery for the MSISDN). Alternatively, ECS 127 may initiate transmit asingle query to GMLC 140 directed to both the location and MSISDN.Additionally, depending on the number of GMLCs, ECS 127 may transmit oneor multiple queries to one or multiple GMLCs 140. In some cases, oneGMLC 140 may provide the location data, while another GMLC 140 mayprovide the MSISDN. According to the various examples just described,the query includes an identifier (e.g., the IMEI). In response toreceiving the query, GMLC 140 performs a lookup for the MSISDN based onthe IMEI (illustrated as lookup MSISDN 243). GMLC 140 transmits aresponse that includes the MSISDN to ECS 127. GMLC 140 also transmitslocation data to ECS 127. PSAP 135 receives the MSISDN and the locationdata (illustrated as receives MSISDN and location data 245). PSAP 135may now use the MSISDN of wireless device 175/user 180 in the event thatthe emergency call gets dropped or disconnected for any reason.

According to various implementations, PSAP 135 may be provided withvarious levels or granularities of location data. For example, one typeof location data may be a cell identifier or cell center. According toanother example, another type of location data may be GPS coordinates(e.g., latitude, longitude). GMLC 140 may obtain location data accordingto well-known or conventional techniques. According to an exemplaryimplementation, GMLC 140 may communicate with an Evolved Serving MobileLocation Center (E-SMLC). The E-SMLC may obtain location data pertainingto wireless device 175 via MME 120-2. For example, a network-basedpositioning procedure or user equipment (UE)-assisted positioningprocedure may be used. According to various implementations, MME 120-2may not transmit the MSISDN according to examples described in relationto FIGS. 2B and 2F. Rather, referring to FIG. 2J, MME 120-2 may transmitthe MSISDN to GMLC 140 in response to receiving location/positioningrequests from GMLC 140 or the E-SMLC. For example, the MSISDN and theIMEI may be carried in a positioning response, along with the locationdata. Depending on the implementation, PSAP 135 may initially beprovided with a coarse level of location data, and subsequently,provided with a finer level of location data by MME 120-2.

Although FIGS. 2A-2J illustrate various embodiments of the emergencycall support service, according to other embodiments, the emergency callsupport service may include an additional step, fewer steps, and/or adifferent step than the steps or operations described. For example,during the establishment of a VoLTE emergency call in which acommunication link between a visiting IMS and a home IMS does not exist,the MME may indirectly provide the PSAP with the MSISDN in response tovarious triggering events. The MSISDN may be carried in various types ofmessages pertaining to the establishment of the VoLTE emergency call.Thus, according to other embodiments, the MME may transmit the MSISDN inresponse to other types of triggering events not specifically describedherein. Additionally, or alternatively, the MSISDN may be carried inother types of messages not specifically described herein.

FIG. 3 is a diagram illustrating exemplary components of a device 300.Device 300 may correspond to various network elements and devicesdepicted in environment 100. As illustrated in FIG. 3, according to anexemplary embodiment, device 300 includes a bus 305, a processor 310,memory/storage 315 that stores software 320, a communication interface325, an input 330, and an output 335. According to other embodiments,device 300 may include fewer components, additional components,different components, and/or a different arrangement of components thanthose illustrated in FIG. 3 and described herein.

Bus 305 includes a path that permits communication among the componentsof device 300. For example, bus 305 may include a system bus, an addressbus, a data bus, and/or a control bus. Bus 305 may also include busdrivers, bus arbiters, bus interfaces, and/or clocks.

Processor 310 includes one or multiple processors, microprocessors, dataprocessors, co-processors, application specific integrated circuits(ASICs), controllers, programmable logic devices, chipsets,field-programmable gate arrays (FPGAs), application specificinstruction-set processors (ASIPs), system-on-chips (SoCs), centralprocessing units (CPUs) (e.g., one or multiple cores), microcontrollers,and/or some other type of component that interprets and/or executesinstructions and/or data. Processor 310 may be implemented as hardware(e.g., a microprocessor, etc.), a combination of hardware and software(e.g., a SoC, an ASIC, etc.), may include one or multiple memories(e.g., cache, etc.), etc.

Processor 310 may control the overall operation or a portion ofoperation(s) performed by device 300. Processor 310 may perform one ormultiple operations based on an operating system and/or variousapplications or computer programs (e.g., software 320). Processor 310may access instructions from memory/storage 315, from other componentsof device 300, and/or from a source external to device 300 (e.g., anetwork, another device, etc.). Processor 310 may perform an operationand/or a process based on various techniques including, for example,multithreading, parallel processing, pipelining, interleaving, etc.

Memory/storage 315 includes one or multiple memories and/or one ormultiple other types of storage mediums. For example, memory/storage 315may include one or multiple types of memories, such as, random accessmemory (RAM), dynamic random access memory (DRAM), cache, read onlymemory (ROM), a programmable read only memory (PROM), a static randomaccess memory (SRAM), a single in-line memory module (SIMM), a dualin-line memory module (DIMM), a flash memory, and/or some other type ofmemory. Memory/storage 315 may include a hard disk (e.g., a magneticdisk, an optical disk, a magneto-optic disk, a solid state disk, etc.),a Micro-Electromechanical System (MEMS)-based storage medium, and/or ananotechnology-based storage medium. Memory/storage 315 may includedrives for reading from and writing to the storage medium.

Memory/storage 315 may be external to and/or removable from device 300,such as, for example, a Universal Serial Bus (USB) memory stick, adongle, a hard disk, mass storage, off-line storage, or some other typeof storing medium. Memory/storage 315 may store data, software, and/orinstructions related to the operation of device 300.

Software 320 includes an application or a program that provides afunction and/or a process. Software 320 is also intended to includefirmware, middleware, microcode, hardware description language (HDL),and/or other form of instruction. By way of example, MME 120-2, ECS 127,GMLC 140, and so forth, may include software 320 pertaining to theemergency call support service, as described herein.

Communication interface 325 permits device 300 to communicate with otherdevices, networks, systems, devices, and/or the like. Communicationinterface 325 includes one or multiple wireless interfaces and/or wiredinterfaces. For example, communication interface 325 may include one ormultiple transmitters and receivers, or transceivers. Communicationinterface 325 may include an antenna. Communication interface 325 mayoperate according to a protocol stack and a communication standard.Communication interface 325 may include various processing logic orcircuitry (e.g., multiplexing/de-multiplexing, filtering, amplifying,converting, modulating, de-modulating, error correction, etc.).

Input 330 permits an input into device 300. For example, input 330 mayinclude a display, a button, a switch, an input port, speech recognitionlogic, a biometric mechanism, a microphone, a visual and/or audiocapturing device (e.g., a camera, etc.), and/or some other type ofvisual, auditory, tactile, etc., input component. Output 335 permits anoutput from device 300. For example, output 335 may include a speaker, adisplay, a light, an output port, and/or some other type of visual,auditory, tactile, etc., output component.

Device 300 may perform a process and/or a function, as described herein,in response to processor 310 executing software 320 stored bymemory/storage 315. By way of example, instructions may be read intomemory/storage 315 from another memory/storage 315 (not shown) or readfrom another device (not shown) via communication interface 325. Theinstructions stored by memory/storage 315 cause processor 310 to performa process described herein. Alternatively, for example, according toother implementations, device 300 performs a process described hereinbased on the execution of hardware (processor 310, etc.).

FIG. 4 is a flow diagram that illustrates an exemplary process 400pertaining to the emergency call support service. Process 400 isdirected to a process previously described above with respect to FIGS.2A-2J and elsewhere in this description, in which the MME obtains theMSISDN of wireless device 175 and provides the MSISDN to the PSAP duringan establishment of an (unauthenticated/anonymous) emergency call.According to an exemplary embodiment, the MME performs some of the stepsdescribed in process 400. For example, processor 310 may executesoftware 320 to perform some of the steps described in process 400. Itmay be assumed that process 400 is performed in a wireless network thatincludes an S8HR architecture in which the home IMS and the visited IMSare not communicatively coupled (e.g., via an Mw interface).

Referring to FIG. 4, in block 405, process 400 begins with receiving anattach request from a wireless device. For example, a visited MME 120 ofa visited network 131 receives an attach request, as a part of anattachment procedure, from a visiting wireless device 175 associatedwith user 180.

In block 410, an MSISDN is obtained based on the attach request. Forexample, the visited MME 120 obtains the MSISDN of the visiting wirelessdevice 175 from HSS 125 of a home network 101. For example, as a part ofan authentication and security procedure, the visited MME 120 uses anidentifier (e.g., an IMEI, etc.) to query HSS 125. In response to thequery, the visited MME 120 obtains the MSISDN. The visiting wirelessdevice 175 attaches to visited network 131. The visiting wireless device175 does not register with a visited IMS 165.

In block 415, a request for an emergency call from the wireless deviceis received. For example, the visited MME 120 receives an emergencyattach request from the visiting wireless device 175. The visited MME120 establishes an emergency PDN connection to a visited PGW of thevisited network 131.

In block 420, a session request is routed to a PSAP. For example, thevisited network receives a SIP Invite from the visiting wireless device175. ECS 127 provides routing information to the visited IMS 165 thatprovides a network address of PSAP 135. The SIP Invite is routed to PSAP135 based on the routing information.

In block 425, a GMLC is queried for the MSISDN. For example, ECS 127queries GMLC 140 for the MSISDN. In block 430, the MSISDN is provided tothe PSAP. For example, ECS 127 receives a response to the query thatincludes the MSISDN. ECS 127 provides the MSISDN to PSAP 135. In block435, the MSISDN is used as a callback mobile number. For example, PSAP135 uses the MSISDN as a callback mobile number to reach user 180 in theevent that the emergency call is dropped or disconnected for any reason.

Although FIG. 4 illustrates an exemplary process 400, according to otherembodiments, process 400 may include additional operations, feweroperations, and/or different operations than those illustrated in FIG. 4and described herein. For example, according to various embodiments aspreviously described, MME 120 may provide the MSISDN based on varioustriggering events (e.g., receipt of a particular message, etc.) and/orduring different stages of a session between the visiting wirelessdevice 175 and the visited network 131.

The foregoing description of embodiments provides illustration, but isnot intended to be exhaustive or to limit the embodiments to the preciseform disclosed. In this regard, various modifications to the embodimentsdescribed herein may be implemented. Thus, specification and drawingsare accordingly to be regarded as illustrative rather than restrictive.For example, although embodiments of the emergency call support serviceinclude operations performed by an MME, according to other embodiments,a Serving General Packet Radio Service (GPRS) Support Node (SSGN) may beimplemented.

The terms “a,” “an,” and “the” are intended to be interpreted to includeone or more items. Further, the phrase “based on” is intended to beinterpreted as “based, at least in part, on,” unless explicitly statedotherwise. The term “and/or” is intended to be interpreted to includeany and all combinations of one or more of the associated items. Theterm “exemplary,” as used herein means “serving as an example.” Anyembodiment or implementation described as “exemplary” is not necessarilyto be construed as preferred or advantageous over other embodiments orimplementations.

In addition, while series of blocks has been described with regard tothe process illustrated in FIG. 4, the order of the blocks may bemodified according to other embodiments. Further, non-dependent blocksmay be performed in parallel. Additionally, other processes described inthis description may be modified and/or non-dependent operations may beperformed in parallel.

The embodiments described herein may be implemented in many differentforms of software and/or firmware executed by hardware. For example, aprocess or a function may be implemented as “logic” or as a “component.”The logic or the component may include, for example, hardware (e.g.,processor 310, etc.), or a combination of hardware and software (e.g.,software 320). The embodiments have been described without reference tothe specific software code since the software code can be designed toimplement the embodiments based on the description herein andcommercially available software design environments/languages.

In the specification and illustrated by the drawings, reference is madeto “an exemplary embodiment,” “an embodiment,” “embodiments,” etc.,which may include a particular feature, structure or characteristic inconnection with an embodiment(s). However, the use of the phrase or term“an embodiment,” “embodiments,” etc., in various places in thespecification does not necessarily refer to all embodiments described,nor does it necessarily refer to the same embodiment, nor are separateor alternative embodiments necessarily mutually exclusive of otherembodiment(s). The same applies to the term “implementation,”“implementations,” etc.

Additionally, embodiments described herein may be implemented as anon-transitory storage medium that stores data and/or information, suchas instructions, program code, data structures, program modules, anapplication, etc. A non-transitory storage medium includes one or moreof the storage mediums described in relation to memory/storage 315.

No element, act, or instruction described in the present applicationshould be construed as critical or essential to the embodimentsdescribed herein unless explicitly described as such.

What is claimed is:
 1. A method comprising: receiving, by a networkdevice of a first wireless network, an attach request from a wirelessdevice to attach to the first wireless network; obtaining, by thenetwork device, a mobile telephone number of the wireless device from asecond wireless network of the wireless device, based on the receivingof the attach request, wherein the second wireless network of thewireless device is communicatively coupled to the first wirelessnetwork; receiving, by the network device, subsequent to an attachmentof the wireless device to the first wireless network, a request toestablish an unauthenticated Voice over Long Term Evolution (VoLTE)emergency call, wherein the wireless device is not registered with afirst Internet Protocol Multimedia Subsystem (IMS) network, which iscommunicatively coupled to the first wireless network, and the first IMSnetwork is not communicatively coupled to a second IMS network of thewireless device; and providing, by the network device, during anestablishment of the unauthenticated VoLTE emergency call, the mobiletelephone number to a public safety access point (PSAP), using the firstIMS network that supports the unauthenticated VOLTE emergency call. 2.The method of claim 1, wherein the providing further comprises:transmitting, by the network device, the mobile telephone number to agateway mobile location center (GMLC) in response to receiving therequest.
 3. The method of claim 1, further comprising: transmitting, byan emergency call server, a query request, which is to a gateway mobilelocation center (GMLC), for the mobile telephone number, based on therequest; and receiving, by the emergency call server, a query response,which is responsive to the query request, from the GMLC, wherein thequery response includes the mobile telephone number.
 4. The method ofclaim 1, wherein the network device is a mobility management entity(MME).
 5. The method of claim 1, further comprising: receiving, by thenetwork device, a location request from a gateway mobile location center(GMLC), and wherein the providing comprises: transmitting, by thenetwork device, a location response that includes the mobile telephonenumber, to the GMLC.
 6. The method of claim 1, further comprising:receiving, by an emergency call server, a query request from the PSAP;and obtaining, by the emergency call server, the mobile telephone numberfrom a gateway mobile location center (GMLC) in response to receivingthe query request.
 7. The method of claim 1, further comprising:storing, by the network device, an identifier of the wireless device andthe mobile telephone number, in response to the obtaining, wherein themobile telephone number is a Mobile Station International SubscriberDirectory Number (MSISDN), and wherein the identifier includes anInternational Mobile Station Equipment Identity (IMEI) of the wirelessdevice.
 8. The method of claim 1, wherein the providing comprises:transmitting, by the network device, the mobile telephone number and anidentifier of the wireless device to a gateway mobile location center(GMLC) in response to receiving the request; receiving, by the GMLC, theidentifier and the mobile telephone number; storing, by the GMLC, theidentifier and the mobile telephone number in response to the receivingof the identifier and the mobile telephone number; and receiving, by theGMLC, a query request for the mobile telephone number, from an emergencycall server, wherein the query request is received subsequent to therequest being routed to the PSAP.
 9. A network, wherein the networkcomprises: a first network device of a first wireless networkcomprising: a first communication interface; a first memory, wherein thefirst memory stores first instructions; and a first processor, whereinthe first processor executes the first instructions to: receive, via thefirst communication interface, an attach request from a wireless deviceto attach to the first network device; obtain, via the firstcommunication interface, a mobile telephone number of the wirelessdevice from a second network device of a second wireless network of thewireless device, based on the attach request, wherein the secondwireless network of the wireless device is communicatively coupled tothe first wireless network; receive, via the first communicationinterface, subsequent to an attachment of the wireless device to thefirst wireless network, a request to establish an unauthenticated Voiceover Long Term Evolution (VoLTE) emergency call, wherein the wirelessdevice is not registered with a first Internet Protocol MultimediaSubsystem (IMS) network, which is communicatively coupled to the firstwireless network, and the first IMS network is not communicativelycoupled to a second IMS network of the wireless device; and provideduring an establishment of the unauthenticated VoLTE emergency call, themobile telephone number to a public safety access point (PSAP), usingthe first IMS network that supports the unauthenticated VOLTE emergencycall.
 10. The network of claim 9, wherein when providing, the firstprocessor further executes the first instructions to: transmit, via thefirst communication interface, the mobile telephone number to a gatewaymobile location center (GMLC) in response to a receipt of the request.11. The network of claim 9, wherein the network further comprises: asecond network device of the first wireless network comprising: a secondcommunication interface; a second memory, wherein the second memorystores second instructions; and a second processor, wherein the secondprocessor executes the second instructions to: transmit, via the secondcommunication interface, a query request, which is to a gateway mobilelocation center (GMLC), for the mobile telephone number, based on therequest; and receive, via the second communication interface, a queryresponse, which is responsive to the query request, from the GMLC,wherein the response includes the mobile telephone number.
 12. Thenetwork of claim 9, wherein the first wireless network is a Long TermEvolution (LTE) network or an LTE-Advanced network, and the firstnetwork device is a mobility management entity.
 13. The network of claim9, wherein the first processor further executes the first instructionsto: receive, via the first communication interface, a location requestfrom a gateway mobile location center (GMLC), and wherein whenproviding, the first processor further executes the first instructionsto: transmit, via the first communication interface, a location responsethat includes the mobile telephone number, to the GMLC.
 14. The networkof claim 9, wherein the first processor further executes the firstinstructions to: store an identifier of the wireless device and themobile telephone number, in response to an obtainment of the mobiletelephone number, wherein the mobile telephone number is a MobileStation International Subscriber Directory Number (MSISDN), and whereinthe identifier includes an International Mobile Station EquipmentIdentity (IMEI) of the wireless device.
 15. The network of claim 9,wherein the network further comprises: a second network device of thefirst wireless network comprising: a second communication interface; asecond memory, wherein the second memory stores second instructions; anda second processor, wherein the second processor executes the secondinstructions to: receive, via the second communication interface, aquery request from the PSAP; and obtain, via the second communicationinterface, the mobile telephone number from a gateway mobile locationcenter (GMLC) in response to receipt of the query request.
 16. Thenetwork of claim 15, wherein the network further comprises: a thirdnetwork device of the first wireless network comprising: a thirdcommunication interface; a third memory, wherein the third memory storesthird instructions; and a third processor, wherein the third processorexecutes the third instructions to: receive, via the third communicationinterface, from the first network device, the mobile telephone numberand an identifier of the wireless device; store the identifier and themobile telephone number in response to a receipt of the mobile telephonenumber and the identifier; and receive, via the third communicationinterface, a query request for the mobile telephone number from thesecond network device, wherein the query request is received subsequentto the request being routed to the PSAP, wherein the second networkdevice includes an emergency call server, and the third network deviceincludes the GMLC.
 17. A non-transitory storage medium storinginstructions executable by a processor of a device of a first wirelessnetwork to: receive an attach request from a wireless device to attachto the device of the first wireless network; obtain a mobile telephonenumber of the wireless device from a second wireless network of thewireless device, based on the attach request, wherein the secondwireless network of the wireless device is communicatively coupled tothe first wireless network; receive subsequent to an attachment of thewireless device to the first wireless network, a request to establish anunauthenticated Voice over Long Term Evolution (VoLTE) emergency call,wherein the wireless device is not registered with a first InternetProtocol Multimedia Subsystem (IMS) network, which is communicativelycoupled to the first wireless network, and the first IMS network is notcommunicatively coupled to a second IMS network of the wireless device;and provide during an establishment of the unauthenticated VoLTEemergency call, the mobile telephone number to a public safety accesspoint (PSAP), using the first IMS network that supports theunauthenticated VOLTE emergency call.
 18. The non-transitory storagemedium of claim 17, wherein the instructions further compriseinstructions to: transmit the mobile telephone number to a gatewaymobile location center (GMLC) in response to a receipt of the request.19. The non-transitory storage medium of claim 17, wherein theinstructions further comprise instructions to: store an identifier ofthe wireless device and the mobile telephone number, in response to anobtainment of the mobile telephone number, wherein the mobile telephonenumber is a Mobile Station International Subscriber Directory Number(MSISDN), and wherein the identifier includes an International MobileStation Equipment Identity (IMEI) of the wireless device.
 20. Thenon-transitory storage medium of claim 17, wherein the instructionsfurther comprise instructions to: receive a location request from agateway mobile location center (GMLC), and wherein the instructions toprovide further comprise instructions to: transmit a location responsethat includes the mobile telephone number, to the GMLC.